Battle.net developer Greg Canessa says that Blizzard is actively working on a LAN-like solution to include for Battle.net play in StarCraft II.

"We are working on solutions with regard to things we can do to maintain connectivity to Battle.net in some way, but also provide a great quality connection between players," said Canessa.
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Blizzard recently announced that traditional LAN play would not be included in the game, with offline play only being allowed in the singleplayer campaign.

I asked Canessa whether the solution his team is working on might include a pseudo-LAN connection, where the game would only check in with Battle.net to authenticate before reverting to typical LAN behavior.

"Something like that," he replied. "Maintaining a connection with Battle.net, I don't know if it's once or periodically, but then also having a peer-to-peer connection between players to facilitate a very low-ping, high-bandwidth connection.. those are the things that we're working on."

Diablo III lead designer Jay Wilson also confirmed that Diablo III will treat LAN in the same way that StarCraft II does, meaning that while traditional offline LAN will not be included in that game, it should support any Battle.net solution developed for the RTS.